Air brake



sePt- 20, 1938- c. A. CAMPBELL. y 2,130,714

' AIR BRAKE Filed April 2, 1958 3 Sheets- Sheet 1 de am? #l Snnentor@Mue/SQL.

f A @@fj G ttornegs Sept. 20, 1938. c. A. QAMPBELL 2,130,714

AIR BRAKE Filed April 2, 1938 I5 Sheets-Sheet 2 Srwentor @Mrz/Em CL@dttornegs Sept. 20, 1938. c. A. CAMPBELL 2,130,714

' AIR BRAKE v Y I Filed April 2, 1958 s shets-sneet 5 Cttornegs vBgPatented Sept. 20, 1938 PATENT OFFICE AIR BRAKE ACharles A. Campbell,Watertown, N. Y., assignor to rihe New York Air Brake Company, acorporation of New Jersey Application April 2, 1938, Serial No. 199,720

9 Claims.

This invention relates to emergency brake pipe vent valves intended foruse in automatic air `brake systems.v Such valves are customarily usedV1in the brake pipe near `the engineers brake valve, but they areavailable for use at any point in the brake pipe at which emergencyventing of the brake pipe may be desired.

`In a prior application, Serial No. 181,040, filed December 21, 1937, Idescribed `and claimed an emergency vent valve of the diaphragm operatedtype and the present invention is in the nature of an improvement on thevent valve of that prior application. i

The principal object of the invention is to secure a vent Valve whichwill operate with a high degree of precision without requiring undulyprecise manufacture and without the use of structural elements which arelikely to stick or become clogged through long continued service.

The structures hereinafter described have a number of importantadvantages. The abutment which is interposed between the usual quickaction chamber and the brake pipe and `which controls the operation ofthe vent valve is a flexible diaphragm hereinafter called the primarydiaphragm. It does not operate the vent valve directly, but on thecontrary admits pressure fluid from the quick action chamber to asecondary motor, also of the flexible ldiaphragm type, to open the ventvalve. Consequently, the load imposed on the primary diaphragm is notheavy but is only that necessary to operate a very simple dual pcppetvalve mechanism.

i Charging of the quick action chamber from the brake pipe is controlledby a small choke. The breathing action, i. e., the reflux from the quickaction chamber to the brake pipe which occurs during service reductions,and serves to prevent emergency response of the primary diaphragm, iscontrolled by another and larger choke. During breathing the chargingchoke, whichis of smaller capacity, is rendered ineffective to limitbreathing iiow by the action of a check valve which opens a by-passaround the charge controlling choke. i

rlhe breathing port which allows reflux from the quick action chamber tothe brake pipe during service is closed by the emergency response of theprimary diaphragm so that all the air in 'the quick action chamber isavailed `of during emergency reductions to operate the brake pipe ventvalve. i

`A ring `shaped filter is interposed between the brake pipe and theactuating mechanism of the vent valve in such a way as to protect allchokes been adopted to facilitate tracing the flows which occur. Thesecond embodiment Which is the preferred form and differs `from the rstchiefly in `the specific arrangement of the secondary motor and ventvalve proper, is shown as it would be commercially constructed.

In the drawings:

Fig. .1 is a sectional view somewhat diagrammatic in character showing avent valve embodying the invention. The valve is shown in charg- `ingand running position.

Fig. 2 is a fragmentary View showing the position assumed by the primary-diaphragm and the lvalves actuated directly thereby in an intermediateposition between the charging or running position of Fig. 1 andemergency position. This l view shows how the breathing port is closedjust prior to the opening of the port which feeds air from the quickaction chamber to the secondary diaphragm chamber.

Fig. 3 is a view similar to Fig. 2 showing emergency position.

Fig. 4 is a plan view of the preferred embodiment of the vent valve.

Fig. 5 is an elevation of the valve shown in Fig. 4, certain passagesand chambers being indicated in dotted lines and the brake pipeconnection being shown in section.

Fig. 6 is a section on the line 6--6 of Fig. 4 drawn on a considerablylarger scale. The mechanism is shown in charging and running position.

Fig. 7 shows a modified port arrangement which may be used to prevent avreversal of the fluid pressure differential acting on the primarydiaphragm. It is shown as a modification of the embodiment of Figs. 1 to3 but can be used in the same way with the embodiment of Figs. 4 to 6.

Referring first to the embodiment shown in Figs. l, 2 and 3, (andparticularly to Fig. l) a supporting bracket is indicated at Il. This isported and receives at one side the union connection I2 for the brakepipe, a portion of which pipe is indicated at I3. Mounted against theother side of the bracket and in` communication with the brake pipe is ahollow casting i4 having passages and chambers hereinafter described,and enclosing not only the quick action chamber generally indicated atI5, but also the various mechanisms making up the vent valve. i Thus,the vent valve and its quick action chamber form a complete structuralunit detachable from the bracket il. The connection is made by studs andnuts, one of which studs, with its nut, is indicated at I 6;

The brake pipe i3 communicates through the port in the bracket II withthe chamber I1. EX- tending across this chamber is a spider I9 which issealed to the casting I4 by two annular gaskets I9 and 2l and serves asa seat for margin of the secondary diaphragm 22, the diaphragm beingclamped to its seat by appropriately formed portions of the cap 23. Thiscap serves as a removable cpver for the body I4 and holds a number ofother parts hereinafter described in assembled relation.

The spider I8 includes a disc-like portion 24 ported at its center,which serves both as a seat for the spring 25 and as a shield to protectthe diaphragm 22 from the blast of air discharging from the brake pipeI3 during emergency venting. This disc 24 is connected by spaced legs 26with the ring shaped portion 21 with which the gasket I9 seals, and thering shaped member 21 carries a seat 28 for the rubber faced vent valve29 which opens outward and which discharges into a downwardly extendingpassage 3l in free communication with the atmosphere.

The diaphragm 22 is of the slack or annularly folded type and iscomposed of any suitable material, preferably a special rubber compoundextensively used for diaphragms in the ail' brake art. It operates thevalve 29 through a stem 32 on which the valve 29 is mounted. The stem 32passes through an aperture in the center of the diaphragm and is clampedto the diaphragm by means of a. flat head 33 formed integrally with thestem and a clamping ring 34 which is forced toward the head 33 by a nut35 threaded on the stem 32. The upper end of the spring 25, which is acompression spring, reacts against the ring 34. The clamp ring 34 isperipherally flanged as shown at 36 to guide the annular fold in thediaphragm 22. The flange 33 coacts with an opposed annular iiange 31 onthe cap 23 to control flexure of the diaphragm and prevent destructivedistortion thereof.

It will be observed that the spring 25 biases the valve 29 in a closingdirection so that in the absence of pressure on the upper side of thediaphragm 22, the valve moves to its seat. Inasmuch as the effectivearea of the diaphragm 22 exceeds the exposed area of the valve 29, brakepipe pressure will hold the valve 29 closed despite its outward openingcharacteristic so long as the 'space above the diaphragm 22 is at, orapproximately at, atmospheric pressure.

The spider I8 is formed with the legs 26 so as not to obstruct thepassage I1. The passage I1 communicates past the spider I8 with thespace 38 surrounding an annular filter element 39. This elementcomprises an annular corrugated frame of foraminous material such aswire gauze or perforated sheet metal covered with any suitable filteringmaterial, for example, wool fabric. Filters of this general. type areextensively used in the air brake art. Any equivalent may besubstituted. The filter 39 seats on an annular bead 4I and its upper endis sealed by a similar annular bead 42 formed on the gasket 43.

The gasket 43 not only seals the filter element 39 but also seals aninsert 44 which serves as a clamping seat for the margin of the primarydiaphragm 45. The marginal portion of the diaphragm functions also as asealing gasket between the insert 44 and the cover 23 previouslydescribed. Thus, when the cover 23 is clamped in place it locks bothdiaphragm assemblies and the filter in place and exerts the pressurenecessary to produce sealing engagement.

Clamped through the center of the primary diaphragm 45 is avalve-carrying hub structure made up of a lower plate 46, an upper plate41, and a sleeve nut 48. The sleeve nut 48 clamps the members 46 and 41upon the center of the diaphragm. The nut 48 is threaded upon a hollowor tubular extension formed on the upper face of the member 46. There isa similar tubular extension on the lower face of the member 46. Theupper tubular extension houses a disc 49 having a central valve 5I ofrubber or the like. This valve is urged upward or outward by a coiledcompression spring 52 and the outward motion is definitely limited by aninwardly directed ange on the nut 48. The valve 5I seats in charging andrunning position against a seat bushing 53 and then closes communicationto a port 54 which leads directly to the space above the secondarydiaphragm 22.

A choke 55 affords a constantly open restricted vent from the spaceabove the secondary diaphragm. This choke 55 is tted with a filtercapsule 56 of felt to protect the choke against clogging without,however, limiting the capacity of the choke, since the felt issubstantially larger than the choke.

The tubular extension on the lower side houses a similar valvecomprising a disc 51 with a central valve 58 urged outward by a coiledcompression spring 59 and limited in its outward motion by the inwardlydirected flange of a sleeve nut 6I. The diaphragm 45 is urged upward bya stabilizing spring' 62 which reacts between the member 46 and theinsert 44. Under charging and running conditions, it holds the diaphragmupward so that valve 5I closes against seat 53 and prevents flow fromthe equalizing chamber I5 to port 54. At such time the space above thesecondary diaphragm 22 is vented to atmosphere through the choke 55.

Upward motion of the primary diaphragm 45 withdraws the valve 58V fromthe seat 63. The valve 58 and its seat 63 control a breathing port 64.The parts are so dimensioned and arranged that if the primary diaphragm45 moves downward in response to an emergency reduction of brake pipepressure, the breathing port 64 will be closed by the valve 58 shortlybefore the passage 54 is opened by the Valve 5I.

The quick action chamber I5 is in free communication with the passage 65which leads to the space above primary diaphragm 45, and is inrestricted communication with the passage 66 through a small chargingchoke 61 which limits the rate of charging of the quick action chamberfrom the brake pipe. A small filter capsule 68 protects the choke 61 andthis choke is mounted beneath a removable plug 69 so that it can beremoved for inspection or replacement without removal of the cover 23.

The breathing port 64 is in communication with the passage 66 by way ofa choke 1I of larger capacity than the choke 61 and designed to controlthe breathing flow, that is, the back flow from the chamber I5 to thebrake pipe during service reductions. This itl does without interferenceby thel choke 61 for the reason that a ball check valve 12 and a rubberseated check valvey 13, arranged in series, permit flow from the passage65 to the passage 66, by-passing the choke 61 but close against ilow inthe reverse direction. Consequently, charging flow from the chamber 38through the filter 39, valve seat 63, passage 64, choke 1| choke 61, iscontrolled as to rate by the choke 61 which is the smallest restrictionin its path. Breathing ow, however, may take place from the chamber I5partly through the choke 6,1 but chiey past the valves 12, 13 andpassage 6,6 directly to the large choke 1I and thence by the passage 64,valve seat 63, lter 39, chamber `38 and passage I1 to the brake pipe. Aremovable cap 1'5` gives access to the check valves.

Thus, the check valves permit a rate of charging flow which is smallerthan the rate of breathing flow. Furthermore, the initial emergencyresponse of the primary diaphragm 45 closes the valve 58. against theseat 33 and arrests. the breathing flow. It does not arrest it atservice reductions because a service reduction will not cause thediaphragm 45 to over-power the spring Operation The main factors ofoperation have been described and only a brief summary is necessary. Ininitial charging, air entering from the brake pipe I3 flows through thepassage I 1` to the chamber 38, and thence through the lter 39, valveseat 63, passage 64, choke 1|, and choke 61 to the chamber I5, chargingthe chamber to brake pipe pressure.,Since the choke 61 is the smaller oftwo chokes in series it imposes the limit onv the charging rate.

After the system is charged a service reduction of brake pipe pressureentails a corresponding reduction of pressure in the chamber A|5 by' wayof check valves 12 and 13 (in parallel with choke 61) to choke 1| whichlimits the rate of back flow. Thence the flow is by passage 64valve seat63, lilter 39, chamber 38 and passage I1 to the brake pipe.

Under all these conditions the valve 29 is held closed by the diaphragm22 and spring 25j.

If the brake pipe pressure is reduced at an emergency rate the back flowlimited by choke 1I is not sufficiently rapid to prevent the developmentof a downward differential on the diaphragm 45 suicient to over-powerstabilizing spring 62. Consequently, the diaphragm moves downward andcloses valve 58 on seat 63 and moves valve 5| from seat 53 so that backflow ,from thequick action chamber is terminated and the quick actionchamber is placed in communication with the space above the secondarydiaphragm 22. Since the pressure above the diaphragm is as high, and infact slightly higher than the pressure beneath the secondary diaphragm,the diaphragm ceases to hold valve 29 closed, so that spring 25 isover-powered by brake pipe pressure acting outward on valve 29. Itfollows that the valve opens wide and vents the brake pipe. The valvewill close after a time interval determinedby the venting capacity ofthe choke 55.

Modified embodiment The commercial structure shown inv Figs. 4 to 6 hasexactly the same operative characteristic as those just described,except that the brake pipe vent valve is urged in a closing direction bybrake pipe pressure, and the opposed face of the secondary diaphragm issubject to atmospheric pressure and not to brake pipe pressure. In thestructure of Figs. 1 to 3vthe secondary diaphragm probably respondssomewhat more rapidly but the device is a little more sensitive toderangement by leakage between valve 29 and its seat.

In Figs. 4 and 5` the hollow casting I I I serves as a combined pipebracket and quick action chamber. It is permanently mounted on the carby means of the studs at its upper end. The union II2 connects the brakepipe ||3 to a cored passage I |1 which leads through the casting, theremainder of the hollow interior of the casting serving as a quickaction chamber H5. 'Ihe main body ||4 of the vent valve proper isclamped to bracket III by the threaded connecters ||6-, so that thebrake pipe chamber |38 communicates with brake pipe passage I I1. Thespace above the primary diaphragm is connected by a port |65 (laterfurther described) with the quick action chamber II5.

The secondary diaphragm |22 is clamped at its margin by a removablecover plate |23, which in this embodiment clamps only the diaphragm |22.To the right of the diaphragm is a curved deflector plate |24 which isfor the purpose of deflecting air discharged through the vent valve, sothat it will not react on the right-hand side of the diaphragm |22. Theseat |28 for the vent valve |29 takes the form of an inserted bushingand the valve is urged to its seat by a coiled compressionspring |25 andalso by brake pipe pressure in the chamber |38. A removable cap ||8sealed bya gasket permits the mounting and the removal of the ventvalve. The vent valve |28 controls flow through the discharge port |3|which leads directly to atmosphere. 'Ihe valve may be forced open bydiaphragm |22 acting through the stem |322 This has a head |35 with aflanged peripheral diaphragm guidingv portion |36. The diaphragm actsdirectly against the head |35 and the flange |36 controls flexure inconjunctionv with the rib |31 of cap |23. The center of the diaphragm isheld against the head |35 by means of a light coil compression spring|26 with a spring seat |21.

The parts so far described involve the chief operative distinctions fromthe structure of Figs. 1 to 3.

The space |38 is in free communication with the space around an annularlter element |39 similar. to the element 39 already described. Thiselement seats at its lower face on a bead |4| and its upper end isengaged by a similar bead |42 formed on the insert |44 which is sealedto the body I |4 bya gasket |43. The member |44` serves as a seat forthe marginal portion of the primary diaphragm |45 which in turn servesas a sealing gasket between the body I I4 and a removable cap I 9.

Clamped through. the center of the primary diaphragm |45 is avalve-carrying hub structure made up of a lower plate |46 and upperplate |41 and a sleeve nut |48. The sleeve nut |48 clamps the members|46 and 41 upon the center of the diaphragm |45, the nut being threadedupon a hollow or tubular extension formed on the upper face of themember |46. A similar tubular extension is formed on the lower face ofthis member. The upper tubular extension houses and guides a disc- |49having a central valve |5Iv of rubber or the like. This valve is urgedoutward by a coiled compression spring |752, its outward motion beinglimited by an inwardly directed ilange on the nut |48. In charging andrunning position the valve 5| seats on and closes the port in a seatbushing |53 and thus interrupts communication between the space aboveprimary diaphragm |45 and a passage |54 which leads to the space at theleft of the secondary diaphragm |22. This space is vented to atmosphereat a restricted rate through a choke |55, shown as protected by a waspexcluder |56.

Ihe tubular extension on the lower side of member |46 houses a valvedisc |51 with a central valve |58 urged outward by a coiled compressionspring I56 and limited in its outward motion by an inwardly directedange on the sleeve nut I6I.

The primary diaphragm |45 is urged upward by a coiled compression spring|62 which is the stabilizing spring and reacts between the member |46and a spring seat |66. This seat |66 is made of pressed metal and iscup-shaped'in form to afford sufficient length to the stabilizing spring|62. It enters the space within the filter element |39.

In the normal upward position of primary diaphragm |45, the valve |58 islifted from its seat I 63.' This valve and its seat control thebreathing port |64. The valves I5I and |58 have the'same characteristicsas the valve 5| and 53, that is, as the diaphragm moves down,overpowering the stabilizing spring |62, it iirst closes the valve |58and then opens the valve I6|. The quick action chamber I|5 is in freecommunication with the space above the primary diaphragm |45 by way ofthe passage |65 which leads through cap II9, body II4, and the wall ofbracket II as indicated in Figs. 5 and 6. The space above the Y primarydiaphragm, and hence also chamber I I5,

is in restricted communication with the space |66 through a smallcharging choke |61 whose function is to limit the rate of charging flowfrom the brake pipe to the quick action chamber. A small lter capsule isassociated with the choke |61.

The breathing port |64 is in communication with the space |66 by way ofa choke I1I of larger capacity than the choke |61 suited to control thebreathing ow already described. A ball Check valve |12 and a rubberseated check valve |13, arranged in series, control ow between the spaceabove the primary diaphragm |45 and the chamber |66, the arrangementbeing such that flow from the brake pipe toward the space above theprimary diaphragm must pass through choke |61, whereas ilow in thereverse direction may by-pass the choke |61 by way of the check valves.Thus, as in the rst described embodiment, the small choke I 61 controlscharging flow, the larger choke V|1| controls breathing iiow, eachwithout interference by the other.

By removing cap I I9 from the body I I4, access to the two flowregulating chokes |61 and I1I is afforded. It will be observed thatchoke |1| is mounted in the body I4 at the junction between body I I4and cap I I9. Access tothe check valves |12 and |13 is had by removing acover plate |15.

Operation of modified embodiment The operation of the device is exactlythe same as` that of the rst embodiment so far as the functions of the`primary diaphragm are concerned. When the primary diaphragm responds toan emergency reduction ofbrake pipe pressure, the breathing port isclosed and quick action chamber air is admitted to the space to the leftof the diaphragm |22. The space to the right is at atmospheric pressure.The diaphragm is of suflicient area to insure the rapid unseating ofvalve |29. The opening of this valve vents the brake pipe and the valvewill be held open for a denite period determined by the venting actionof choke |55.

The commercial structure has certain advantages. In the rst place, thepipe bracket contains the quick action chamber and the connecting portto the vent valve. This can remain attached to the car While the entirevent valve structure may be removed as a unit by releasing the threadedconnecters I I6. Removal of the caps |23 and II8 give access to thesecondary diaphragm mechanism and to the vent valve while the removal ofcap I I9 gives access to all the moving parts of the mechanismsassociated with the primary diaphragm. The structure is simple,extremely compact, and when constructedv with an ordinary commercialdegree of accuracy will operate with remarkable precision over a longperiod of time without adjustment or even inspection.

Alternative porting-Fig 7 Since the primary diaphragm mechanism of Figs,l to 3 is functionally identical with that of Figs. 4 to 6, and sincethediagrammatic showing of Figs. l to 3 is easier to follow, Fig. 7 hasbeen drawn on the basis` of Figs. 1 to 3, but the porting can besubstituted in the same way in Figs. 4 to 6.

In Figs. 1 to 6 control of the fold in the primary diaphragm is effectedby the marginal contours of diaphragm clamping members, soy thatreversal of the pressure differential which tends to occur duringcharging is tolerable in many cases. The porting in these figures issuch as to permit it toV occur.

Fig. 1 shows how the scheme used in my prior application aboveidentified can be used to preclude such reversal of pressuredifferential. The same reference numerals are used as in Figs. 1 to 3but with the distinguishing letter a.

The changes from the structure of Figs. 1 to 3 are merely that (l) port66a does not lead to the space above primary diaphragmY 45a, and port66a does lead to this space.

Consequently, during charging, choke 61a develops back pressure actingagainst the upper side of diaphragm 45a approximately equal to Y brakepipe pressure` acting against the lower side. VChoke lia, beingcomparatively large, has no material ilow restricting effect.

During breathing the ilow is from the quick action` chamber through thecheck valves as before. rIhe slightly different connection to the spaceabove the diaphragm has no functional signiflcance. Elimination of theresistance of the check Valve to flow from this space is beneficial sofar as it has any effect.

In emergency, flow from the quick action chamber to the space above theprimary diaphragm and thence via passage 54a to the secondary diaphragmmust pass check valves 12a, 13a. Hence in Fig. '7 the check valvescannot be as small as they might be in Figs. 1 to 6J but since theycannot conveniently be made of the minimum size permissible for thestructure of Figs. l to 6, and can easily be made as .large as necessaryfor the arrangement of Fig. 7 this difficulty is not serious',

Commercially the check valves would be of about the size shown in eithercase, which is conditions.

lar-ge enough for Fig. 7 and larger than strictly necessary for Figs. 1to 3 (for example).

- 'I'he choice of porting depends on particular For the general run ofcommercial installations Fig. 6 is preferred.

General considerations Each of the various arrangements above eX-plained is characterized by accurate control and proper differentiationof charging and breathing flows. The primary diaphragm operates smalland simple valve mechanisms which are completely enclosed and hencefully protected. This diaphragm does not require precise guiding. Inemergency functions all of the quick action chamber air passes to andthrough the secondary diaphragm chamber and hence is usefully applied.The secondary diaphragm motor is easily made of adequate size but ofsmall enough clearance to ensure certain rapid action and economical useof air.

'Ihe construction is simple, involves no undue number of parts, and nonerequiring very precise manufacture. It is easily assembled anddismounted, requires no adjustments, and is very compact.

While I prefer the embodiments shown, these are to be taken asillustrative and not limiting.

What is claimed is:- y

1. 'I'he combination of a brake pipe; a normally closed brake pipe bentvalve; means forming a quick action chamber and a brake pipe chamber,the latter in communication with the brake pipe; a iexible diaphragminterposed between said chambers; motor means rendered active bysubstantial displacement `of said diaphragm toward said brake pipechamber to cause opening of said vent valve; yielding means resistingsuch displacement; means including a pair of restricted chokes affordingcommunication between brake pipe and quick action chamber; one way flowvalve means for inhibiting the controlling action of one of said chokes,whereby a differential is established between theY rate of char-gingflow toward and breathing flow from said quick action chamber; and valvemeans rendered effective by motion of said diaphragm toward the brakevalve chamber, at least as soon as said vent valve opening `means iscaused to operate, to arrest breathing flow from said quick actionchamber.

2. The combination defined in claim 1 in which said chokes are arrangedin series and the one way flow valve means opens a by-pass around thesmaller thereof.

3. The combination with the structure defined in claim 1 of an annularfilter substantially concentric with the diaphragm and interposedbetween said brake pipe chamber and the brake pipe; and an annularmember which serves as a seat for the periphery of the diaphragm and asealing retainer for said filter.

4. The combination of a brake pipe; a normally closed brake pipe ventvalve; a pressure motor having a restricted vent, said motor serving toopen said vent valve when pressure is developed therein; means forming aquick action chamber and a brake pipe chamber, the latter incommunication with the brake pipe; a flexible diaphragm interposedbetween said chambers; a pair of controlling valve mechanisms onopposite sides of said diaphragm, each comprising a ported seat and acoacting poppet valve yieldably mounted on the diaphragm, such mountingincluding means to limit motion of the valve toward the seat relativelyto the diaphragm, whereby the valves open selectively as the diaphragmmoves reversely; a connection from the quick action chamber to saidmotor controlled by one of said valves; yielding means urging thediaphragm in a direction to close the valve just mentioned; a chargingand breathing connection controlled by the other valve; and meanscomprising two chokes and a check valve for establishing a differentialbetween the rate of charging ow through said connection toward saidchamber, and the rate of breathing iiow in the reverse directiontherethrough.

5. The combination defined in claim 4 in which the pressure motor is ofthe diaphragm type, single acting, and the vent valve is a poppet valveurged in a closing direction by brake pipe pressure.

6. The combination defined in claim 4 in which the vent valve is apoppet valve urged in an opening direction by brake pipe pressure, andthe pressure motor is of the double acting diaphragm type, has aneffective area larger than` that of the vent valve, and is subject in avalve-closing direction to brake pipe pressure.

7. The combination defined in claim 4 in which the chokes and checkvalve are so arranged that the smaller charge controlling choke is atthe entrance to the quick action chamber and holds an approximatelyequalized back pressure on bothl sides of the diaphragm during charging,and the check valve permits rapid iiow by passing both chokes from thechamber to the controlling valve associated with the vent valve motor.

8. The combination with the structure of claim 4 of plates clamped tothe central portion of the diaphragm, the diaphragm being of the typehaving an annular fold and the plates being formed to control said foldas the diaphragm moves and also serve as the sole guiding means for thediaphragm and the associated control valves.

9. The combination of a brake pipe; a normally closed brake pipe ventvalve; means forming a quick action chamber, a diaphragm chamber and abrake pipe chamber the latter in free communication with the brake pipe;a flexible diaphragm interposed between the diaphragm chamber and thebrake pipe chamber; a flow controlling choke establishing restrictedcommunication between the brake pipe and diaphragm chamber; a smallerflow controlling choke establishing a charging communication from thediaphragm chamber to the quick action chamber; one-way flow valve meansfor permitting flow unlimited by the last named choke from the quickaction chamber to the diaphragm chamber; motor means rendered active bysubstantial motion of said diaphragm toward the brake pipe chamber toopen said vent valve; Valve means rendered operative by less motion ofthe diaphragm in the same direction to close communication between thebrake pipe and diaphragm chamber; and yielding means resisting motionofthe diaphragm toward the brake pipe chamber.

CHARLES A. CAMPBELL.

